The rotational speed of the alternator used in vehicles can be increased by using a poly V belt as the driving means. In order to realize such a high speed alternator, it is necessary to make the structure of the generator firm so as to reduce flection of the axis of the generator, to reduce vibrations of the generator, to give the generator an excellent centrifugal force characteristic, and hence to make the generator competent to withstand the high speed rotation. Also, it is necessary to provide an excellent cooling system in which stator windings, rectifiers, a regulator of the integral circuit type, rotor winding and bearings can be cooled in a suitable manner. Further, it is necessary to reduce the noise of the generator when rotating, which noise arises from the friction between the blades of the cooling fan in the generator and the air.
The present invention is directed to improve the structure of the alternator so as to comply with the above described requirements for the high speed rotation of the alternator.